It is known, lidar signal intensity due to double scattering depends on the particle size distribution of under investigation aerosol formation. The most sensitive to microstructure of sounding aerosol is lidar signal component, which is defined by diffraction component of the phase function. Analytical expressions for return scattering radiation received from aerosol cloud at different distances are analyzed in this report. Also possible methods of extraction from lidar signal sensitive to microstructure sounding aerosol component are considered. Theoretical analysis results are reported.